Synchrotronstrahlung

The Helmholtz-Zentrum Geesthacht Outstation at DESY

GEMS currently participates in the operation of four beamlines at PETRA III synchrotron storage ring at DESY. The High Energy Material Science Beamline (HEMS) and the Imaging Beamline (IBL) are optimized for material science applications forming a unique research cluster. Due to the complementarity in their energy ranges and beam properties, the beamlines provide facilities for a large range of diffraction and imaging experiments to a widespread user community. GEMS participates also in the operation of the BioSAXS beamline of EMBL at PETRA III and can hence offer also a characterization method for the study of nanostructured materials. The variety of available techniques is completed by the scattering methods available at the Nanofocus endstation, which HZG operates in collaboration with DESY and Kiel University at DESY beamline P03.

The DORIS III storage ring was shut down on October 22, 2012. However, HARWI II will be moved to the PETRA III extension facility as HARWI III.

Figure 1: Beamline layout

The high-energy beamline HARWI-II was dedicated to texture, strain, and imaging measurements for materials science. The beamline layout including the beamline optics, the experimental stations, and the control hutch are presented in figure 1.

Instrument description:

Front-end filter:

3 mm Carbon is permanently installed as a high pass filter in order to reduce the heat load onto the monochromator. For the hard X-ray options additionally either a 1 mm thick and 10 mm wide or a 2 mm thick and 70 mm wide copper filter can be inserted into the beam path. Both Cu filters withstand the thermal load with 10 mm carbon in front.

Monochromator setup:

Figure 2: Sketch of the monochromator setup

The monochromator tank (figure 2) accommodates two different types of monochromators. The first type of monochromator (type A) is a double Laue monochromator in horizontal geometry for strain and stress analysis and delivers beams of 10 mm ×10 mm in size. Both goniometers can hold a set of crystals. Using another pair of crystals is accomplished by linear stages on top of the goniometers. With the currently installed tempered Si(111) crystals an energy range of 65 - 200 keV can be reached with a dynamical rockimg width of 6 arcsec at 100 keV. The second monochromator is optimized for imaging experiments. This monochromator produces a beam size of up to 70 mm x 10 mm in a vertical diffraction geometry. The energy range will be 20 to 150 keV. Furthermore a direct white beam of about 0.5 mm x 0.5 mm can be provided for experiments.

Experiments:

Figure 3: Heavy duty diffractometer

In the experimental hutches three pits are lined up along the beam. The pits houses the different experiments. One of the experiments is a heavy duty diffractometer which is specially designed for high photon energies studies. The diffractometer isinstalled in pit 1 (see figure 1).

Figure 4: Detector portal

It is equipped with various translation, rotation, and tilt stages. The tower is large enough to carry heavy samples and heavy user environments up to 600 kg. The incoming and scattered beam can be defined by slit systems attached to the diffractometer. Diffracted photons can be detected with two position sensitive two-dimensional gas-wire counter each with an active area of 300 mm × 300 mm. The detectors can be mounted on two 2θ-arms for scattering in the vertical plane. The sample-detector distance is adjustable via additional translation stages which are mounted on the diffractometer arms. In addition, the detectors can be mounted on a large movable frame (see figure 4) in order to position them at any desired location behind the sample.

Figure 5: The INSTRON stress rig

The maximum sample-detector distance can be up to 9 m. Thus measurements with high angular resolution can be performed. An energy-dispersive detector, a scintillation counter and image plate scanner are also available. Moreover, a flat panel detector is ordered. In order to perform in-situ residual stress analysis experiments an INSTRON stress rig (see figure 5) was set up. It works servo-hydraulically and is equipped with water-cooled clamps. The rig can be used in-situ or ex-situ, i.e. for long term experiments.

The second permanent experiment is a tomography station which is installed onto a lift table (figure 1 position 3). The tomography camera mainly consists of an efficient X-ray detector and a high-precision sample-manipulator stage. The two dimensional X-ray detector is specially equipped to detect the high-energy X-ray beam. The system is designed to operate with photon energies from 20-150 keV. Using an optic with variable focus the field of view can be adapted to the diameter of the investigated sample. Thus, spatial resolution up to 2 μm can be achieved by the tomography system. The sample-manipulator provides a high precision rotation, translation and reposition of the sample.

High Energy Materials Science Beamline at PETRA III

Hems

The High Energy Materials Science Beamline HEMS at PETRA III has a main energy of 100 keV, tunable in the range 30 to 200 keV, and is optimized for micrometer focusing with Compound Refractive Lenses (CRLs).

Design, construction, operation and main funding are the responsibility of the Helmholtz-Zentrum Geesthacht. Approximately 70 % of the beamtime is dedicated to Materials Research, the rest reserved for "general physics” experiments supported by DESY.

The materials science and general physics activities are threefold:

1) Fundamental research encompasses metallurgy, physics, chemistry, biology etc. which are more and more merging. Experiments had been done for the investigation of the relation between macroscopic and micro-structural properties of polycrystalline materials, grain-grain-interactions, recrystallisation processes, the development of new & smart materials or processes, and in situ catalysis mechanisms. Generally, all kinds of matter can be studied with high precision, high stability and low background: surfaces, interfaces, bulk single crystals, powders as well as amorphous materials in a large reciprocal space.

2) Applied research for manufacturing process optimization benefits from high flux in combination with fast detector systems allowing complex and highly dynamic in-situ studies of microstructural transformations, e.g. during welding and loading processes. The beamline infrastructure allows easy accommodation of large user provided equipment, such as an in-situ friction stir welding device which has been built at Helmholtz-Zentrum Geesthacht.

3) Experiments targeting the industrial user community are based on well established techniques with standardised evaluation, allowing "full service" measurements. Environments for strain mapping on large structural components up to 1 t will be provided as well as automated investigations of large sample numbers, e.g. tomography and texture determination.

The experimental hutches EH2 and EH3 have been available for reviewed user experiments since 2011. EH4 with its micro-tomography set-up was commissioned in 2012 (absorption) and 2013 (phase contrast), and its mapper set-up in the second half of 2013. The Test Facility EH1 is not available for external users.

Micro and Nano Tomography

IBL - Beamline

The development of new materials highly demands the study of their three dimensional inner structures. Thus, in particular tomographic evaluation methods gain more and more importance in the materials characterization field. Characteristic length scales, which influence the structural properties, are often in the range of some micrometers down to a few nanometers.

Due to the extraordinary high brilliance of the new storage ring PETRA III, the extremely low emittance of 1 nmrad and the high fraction of coherent photons even in the hard X-ray range an extremely intense and sharply focused X-ray light is provided.

Therefore, the Helmholtz-Zentrum Geesthacht takes active part in the PETRA III project by operating and funding the Imaging Beam Line (IBL). This beamline is optimized for micro and nano tomography applications.

The Imaging Beamline (P05) consists of a two meter undulator source, an optics hutch (OH) including two monochromators (DCM and DMM) and two independent experimental hutches EH1 and EH2 working alternatively.

BioSAXS Beamline at PETRA III

EMBL – in cooperation with scientists at the Helmholtz-Zentrum Geesthacht – has built a SAXS beamline oriented towards biology/soft condensed matter.

It will provide a wide range of spatial resolutions from about 0.1 nm to 2000 nm and operate in the energy range from 4 to 20 keV.

The focal spot on the detector is 0.2 (horizontal) x 0.1 (vertical) mm.

The flux on the sample is in the order of 1013 at wavelength resolution 3*10-4 with a double crystal monochromator and is calculated to be 1015 at wavelength resolution 1*10-2 for a possible pink beam or multilayer option in the future.

The sample environment unit on BioSAXS at PETRA III allows fast mixing of solutions for time resolved measurements and automatic change of samples. For fast screening, a robotic sample loading (5-20 μL and filling cycle 20 sec) is incorporated at the beamline using a device which was constructed in collaboration between EMBL (outstations in Grenoble and Hamburg) and ESRF.

The design of the instrument is shown in Fig. 1. The contribution of Helmholtz-Zentrum Geesthacht was the construction of the 5 m detector stage which allows recording of different angular regimes by automatically changing the sample-to-detector distance within minutes.

High quality scattering patterns are recorded with a modern PILATUS 2M single photon counting pixel detector. This detector combines a high dynamic counting range with low noise readout.

Small-angle X-ray scattering data on several biological and biocolloidal systems at very low volumes can be collected at the beamline. For future SAXS experiments with ultra-small sample volumes (< 1 nanoliter), microfluidic sample environments and fast mixing by stopped-flow technique are under development.

Helmholtz-Zentrum Geesthacht is in charge of 15 % of the total beam time at BioSAXS. The beamline is supported by personnel of the Helmholtz-Zentrum Geesthacht and by contribution to the operation costs.

Beside soft matter experiments which are possible at our SANS instrumentation at GEMS, a strong focus is on materials science related research (e.g. bio-membranes) which complements the protein and biomacronolecules focussed work of EMBL.

Nanofocus endstation at DESY beamline P03 at PETRA III

Fig 1: Nanofocus Endstation at P03 beamline at PETRA III

Scanning X-ray nanodiffraction (SXND) is an excellent tool for materials science. It provides structural information with sub-µm resolution from crystalline and semi-crystalline materials (e.g. metals, biomaterials, synthetic compounds). That way grain orientation, residual stress profiles, crystal structure or texture can be obtained in a nondestructive analysis. The Nanofocus Endstation of P03 (MINAXS) provides conditions for SXND even in extended in situ sample environments, due to the long focal distance of the used X-ray optics and the high X-ray energy that is available at the beamline. The nanofocus endstation started operation end of 2010 and steeply increased on user dedicated beam time since, reflecting a high operational efficiency despite the competitive mode of beam time distribution between the two P03 endstations. The beamline P03 and the microfocus endstation of it are operated by DESY (beamline manager Stephan Roth) while the Nanofocus endstation, constructed within a BMBF-funded project by Kiel University, is now operated by Helmholtz-Zentrum Geesthacht in cooperation with Kiel University and DESY.

A nanobeam with a size of typically 350 x 250 nm2 is generated using a nanofocusing mirror system with a large focal length of 10 cm. New techniques, using this capacity, are constantly being developed at P03 with a strong focus on material science in order to promote the use of SXND in materials science. 2D X-ray waveguide based focusing is also available for smaller beams. The endstation offers a beam size of 250 nm and an energy in the range 8 - 23 keV.

A clear working distance of 8 cm provides an excellent setting for materials science because it accepts extended in situ sample environments. Experiments at the endstation have used constructions to control for pressure, E/B fields, temperature, fluid shear, tension or indentation force in situ in nanodiffraction experiments. Sample alignment is eased by up to three video microscopes and precision of up to 10 nm for positioning the sample is possible on a set of hexapods.